Photoelectronic safety device

ABSTRACT

A photoelectronic safety device for connection to a three phase electrical supply line feeding a user apparatus. This device comprises at least three lamps star connected to the supply line, at least one photoresistance facing the lamps and emitting an outlet signal in response to the variations of luminosity of the lamps, amplifier means controlled by the outlet signal, and switching means in the supply line controlled by the amplifier means and adapted to disconnect the user apparatus from the line.

it atnt r 1 Zizola 1 Sept. ii, i973 i 1 PHOTOELECTRONTC SAFETY DEVllClE [76] Inventor: Giuseppe Zizola, c/o Zanfranceshi Via Longhin l Treviso, Ponzano, Italy 22 Filed: Sept. 29, 19711 211 Appl.No.:184,806

[30] Foreign Application Priority Data Oct. 1, 1970 Italy 82525 A/70 Apr. 29, 1971 ltaly 82517 A/71 [52] 11.8. C1 317/31, 250/214, 307/311, 317/33 SC, 317/48, 317/54, 324/96 [51] llnt. Cl. 111021: 3/28 [58] Field ot Search 340/190; 324/96,

[56] lRelierences Cited UNITED STATES PATENTS 2,038,277 4/1936 Gent 1 324/96 3,467,858 9/1969 Burnett 324/96 I09 L A 112 08 3,483,429 12/1969 Engel 307/311 3,141,131 7/1964 McCoy 324/96 3,331,022 7/1967 Maione .1 324/96 3,346,811 10/1967 Perry 324/96 3,461,384 8/1969 Bayati.... 324/96 3,485,940 12/1969 Perry 324/96 Primary Examiner-James W. Lawrence Assistant Examiner-D. C. Nelms Attorney Guido Modiano and Albert .losif [57] ABSTRACT A photoelectronic safety device for connection to a three phase electrical supply line feeding a user apparatus. This device comprises at least three lamps star connected to the supply line, at least one photoresistance facing the lamps and emitting an outlet signal in response to the variations of luminosity of the lamps, amplifier means controlled by the outlet signal, and switching means in the supply line controlled by the amplifier means and adapted to disconnect the user apparatus from the line.

1 Claim, 3 Drawing Figures PATENTEUSEPI H 3,758,826

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INVENTOR GIUSEPPE ZIZOLA BY I I 509% AGEN I PHOTOELECTRONIC SAFETY DEVICE BACKGROUND OF THE INVENTION The present invention relates to a photoelectronic safety device for industrial and domestic electrical installations.

Various devices are available for the protection. both of machinery operators and of the machines themselves. Said devices are based on mechanical, electromagnetic, electronic and other operating principles.

These conventional devices often give rise to disadvantages of which the most serious is that of a too lengthy intervention time, i.e. in these conventional safety devices the time interval between the instant in which the operating fault or irregularity arises and the instant in which the safety device cuts out the apparatus to be protected is excessive.

This delay in intervention can cause serious accident to personnel and considerable damage to machinery.

Conventional safety devices sometimes give rise to difficulties of calibration, which may cause either an absence of intervention when needed or an untimely intervention which constitutes an unnecessary suspension of production, giving rise to increased costs.

A further disadvantage is that the operation of said conventional safety devices is often influenced by the loading both of the feed line and of the machinery to be protected, and by instantaneous variations in utilisation.

Moreover said devices are often of complex construction, high cost and difficult application, and require accurate maintenance.

SUMMARY OF THE INVENTION The main object of the present invention is to eliminate the aforementioned disadvantages of conventional types of safety and protection devices by providing a photoelectronic safety device which allows efficient and reliable protection to be obtained under any loading condition.

A further object of the present invention is to guarantee instantaneous disconnection from the line of the user apparatus downstream of the photoelectronic safety device whenever for any reason Contact is made between one phase and earth, orbetween two phases or when there is an interruption or irregularity in the circuit of the device.

A further object of the present invention is to provide a device consisting of a minimum number of components, which requires little maintenance and which allows easy and rapid restoration of operating conditions once the cause or causes which have led to interruption of service have been eliminated.

A further object isv to provide a photoelectronic safety device which may be easily and rapidly connected to the line or apparatus to be protected.

A furtherobject of the present invention is to provide an easily calibrated device sensitive even to slight faults.

- These and further objects are attained by the photo electronic safety device for connection to a three phase electrical supply line feeding a user apparatus, said device comprising at least three lamps star connected to said supply line, at least onephotoresistance facing said lamps and emitting an outlet signal in response to the variation in luminosity of said lamps, amplifier means controlled by said outlet signal from said photoresistance or photoresistances, and switching means in said line controlled by said amplifier means and adapted to disconnect said user apparatus from said line.

BRIEF DESCRIPTION OF THE DRAWINGS Further characteristics and advantages of the invention will become more evident from the description of two preferred but not exclusive embodiments of the photoelectronic safety device for industrial installations, illustrated by way of example in the accompanying drawings in which:

FIG. I is the operational schematic diagram of one embodiment of the device;

FIG. 2 is the operational schematic other embodiment of the same device;

FIG. 3 is a diagrammatical representation of the device whose schematic diagram is shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, the device comprises a housing, not shown in the Figures, inside which is assembled a circuit 1 connected to the terminal block 100, and which connects together the various components of the device as determined by the schematic diagram.

Said circuit 1 comprises three sealed neon lamp photoresistance units 2, each formed from a neon lamp 3 facing a corresponding photoresistance 4.

Said, lamps 3 are star connected and shunted across the line (101, 102, 103), and the star centre 104 is connected to the earthed casing of the user machine 11. The three photoresistances 4 are connected together in series and the two end terminals are connected one to the anode 202 of the TRIAC (5) and the other to the gate 203. The variable resistances I3, placed before each lamp 3, carry out the double purpose of adjusting the lamps 3 to the supply voltage and determining the level of sensitivity of the apparatus.

A relay 6 controlling the switch 7 is connected at one terminal to the anode 202 of the TRIAC 5 and at the other terminal to the mains supply for example of 380 V, by way of the connection 15. If the three phase supply is for example 220 V the connection to the mains supply is made by the bridge 14 and the contact 15 is eliminated.

A pushbutton 8 connected in the control circuit of a coil 9 determines the closing of a contactor l2 and a remote control switch 10. Operation of the photoelectronic safety device shown in FIG. 1, which may be coupled to a user apparatus 11, is as follows. Under normal operating conditions the neon lamps 3 are alight and the light produced by them strikes the photoresistances 4, which as their ohmic value diminishes allow a current to pass of such an intensity that when applied to the gate 203 of the TRIAC 5 it puts the TRIAC 5 into the conduction state.

Under these conditions the circuit energises the relay 6 and the corresponding switch 7 closes.

If the pushbutton 8 is now pushed the coil 9, which is connected as shown in the schematic diagram to the terminals 109, 112 and 1108, becomes energised and the contactor 12 of the remote control switch 10 is closed and the supply becomes connected to the user apparatus ll placed downstream of said remote switch 10.

The coil 9 of the remote control switch It) continues to be energised even when pressure on the pushbutton diagram of an- 8 ceases,"because it is self energised by way of the contactor 12.

if contact takesplace between one phase and the casing of the machineprotected by the device, or between two or more phases, or if one phase becomes earthed .downstream of the safety device, the following modifications take place: the lamps. 3 corresponding to the phases associated with the fault are either extinguished or the intensity of the light emitted by them diminishes, with a consequent increase by photoelectric effect of the total resistance of the photoresistances 4 and a corresponding diminution in the current circulating through said photoresistances 4. When said current, which kept the TRIAC 5 in the conduction state by way of the gate 203, diminishes the TRIAC 5 becomes deenergised and the relay 6 opens together-with the corresponding contacts 7.

When the contacts 7 open the supply to the coil 9 ceases, with consequent opening of the remote control switch 10 and contactor 12. Under these conditions the load is disconnected from the line (101, 102, 103).

If the fault arising is only momentary, the supply to the user apparatus 11 can be restored by again pushing the pushbutton 8.-lf however the fault is permanent, the device continues to cut out when pushing the pushbutton 8 and hence in order to restore operating conditions it is necessary to wait for elimination of the fault.

FIGS. 2 and 3 show another embodiment of the photoelectronic safety device for industrial and domestic electrical installations.

The device consists of a container 300 containing the circuit 20 comprising units 301 and 302 each formed from three sealed cells 21. Each cell 21 contains a neon lamp 22 facing a photoresistance 23. Said lamps 22 are star connected between each of the three phases 101,

102,103 and the neutral wire-104, whereas the photoresistances 23 are connected together in series.

The end terminals of the series resistances 23 are connected'to anamplifier circuit 24. Said circuit 24 comprises a transformer 25 which through a rectifier 26 supplies a printed circuit 27, which in its turn feeds the coil 28 which acts on the contacts 29. A potentiometer- 30 suitably calibrated during the testing stage is also provided and adjusts the sensitivity of intervention of the safety device. i

The pushbutton 31, connected into the circuit of the coil 32, controls the closing of the contactor 33 and remote control switch 34, and the consequent supply to the user'apparatus 35. If an operational defect arises within the fault detector unit 301, the unit 302 is switched in bymeans of a commutator 40, and the unit 301 is disconnected. Obviously if a fault arises in unit 302 it is possible to switch in the unit 301.

Two indicator lamps 41 and 41a coloured red and green respectively indicate which of the units 301 and 302 is connected.

Operation of the photoelectronic safety device for industrial and domestic electrical installations, applied upstream of a group of user apparatus or where appropriate to each single user apparatus, is as follows: the lamps 22 connected to the line 101, 102, 103 are alight, and the light produced by them strikes the photoresistances 23, which as their ohmic value diminishes, allows a current to pass of an intensity suchthat when suitably amplified by the printed circuit 27 it is capable of energising the coil 28 which in its turn closes the contacts-29.

Because of the considerable power absorbed by the user apparatus it is not possible to use said contacts 29 for general remote control switching purposes. Consequently said contacts serve only for acting on the supply circuit to the coil 32.

. if the pushbutton 31 is now pressed, the coil 32 is energized and causes the closure of the contactor 33 and general remote control switch 34.

The coil 32 of the remote control switch 34 continues to be supplied even when pressure on the pushbutton 31 ceases, because it is self-fed by way of the contactor 33.

Once the safety device upstream'of the remote control switch 34 has been switched on, if contact occurs between one phase and earth or between two phases, the immediate consequence will be a diminution in the luminous intensity which strikes the photoresistances 23, causing diminution in the current which flows through said resistances and consequently a diminution in the current at the outlet of the printed circuit 27.

The current intensity at the outlet of the circuit 27 in the case of a fault is such that the coil 28 is no longer able to maintain the contacts 29 closed.

The opening of the contacts 29 causes the deenergising of the coil 32 and hence opening of the contactor 33 and the general remote control switch 34, with consequent disconnection of the user apparatus 35 from the line (101, 102, 103, 104).

When the causes of the fault have been removed the pushbutton 31 is again pressed, which by energising the coil 32 causes the remote control switch 34 to close and the consequent connectionof the user apparatus 35 to the line.

The invention so conceived is susceptible to numerous modifications all of which fall within the scope of the inventive idea.

I claim:

1. In a photoelectronic safety device for disconnecting a 'user apparatus from a supply line by means of a remote-control switch when faults or irregularities arise in the line, the user or the safety device, the combination comprising:

photoelectric means connected to the supply line and including at least three lamps star connected and shunted across said supply line, the star center of said star connection of said lamps being grounded, and at least three photoresistances connected together in series and each facing one of said lamps, said photoresistances being responsive to the light signal emitted by said lamps and to the variations of said light signal, an electronic controlled switch v including a TRIAC having a gate connected to one end of said series of photoresistances and an anode connected to the other end of said series of photoresistances,

a relay connected between said anode and said supply line and controlled by said TRIAC,

a control circuit including a switch controlled by said relays, a manually operable push button, a contactor and a coil for operating said contactor, said contactor controlling said remote control switch provided on said supply line, and said coil being connected between said push button and the cathode of said TRIAC,

and adjustment means for said lamps for adjusting said light signal emitted by said lamps and determining the level of sensitivity of the device.

4 i i l 

1. In a photoelectronic safety device for disconnecting a user apparatus from a supply line by means of a remote-control switch when faults or irregularities arise in the line, the user or the safety device, the combination comprising: photoelectric means connected to the supply line and including at least three lamps star connected and shunted across said supply line, the star center of said star connection of said lamps being grounded, and at least three photoresistances connected together in series and each facing one of said lamps, said photoresistances being responsive to the light signal emitted by said lamps and to the variations of said light signal, an electronic controlled switch including a TRIAC having a gate connected to one end of said series of photoresistances and an anode connected to the other end of said series of photoresistances, a relay connected between said anode and said supply line and controlled by said TRIAC, a control circuit including a switch controlled by said relays, a manually operable push button, a contactor and a coil for operating said contactor, said contactor controlling said remote control switch provided on said supply line, and said coil being connected between said push button and the cathode of said TRIAC, and adjustment means for said lamps for adjusting said light signal emitted by said lamps and determining the level of sensitivity of the device. 